Extrusion die

ABSTRACT

This invention relates to extrusion dies useful for processing both non-ferrous metals and alloy steels, the dies being made of a predominant amount of molybdenum or tungsten, the remainder being zirconia.

Unite tates Patent Heitzinger 1 1 Feb. 12, 1974 1 1 EXTRUSION DIE2,798,808 7/1957 lrcdell ct =11 75/206 [75] Inventor: Friedrich FranzXaver Heitzinger, FOREIGN PATENTS OR APPLICATIONS Lechflschau, Austria1,242,810 6/1967 Germany [731 Assignee: Schwarzkopf Development OTHERPUBLICATIONS Corporation New York Goetzel, Treatise on PowderMetallurgy, 1950, Vol 11 [22] Filed: Jan. 29, 1971 pp. 685, TN695 60,lntersci'ence Pub. [21] Appl No; 111,136 Harwood, The Metal Molybdenum,ASM, 1958, pp.

25-27, 29 & 30, TN799 M7U55.

[30] Foreign Application Priority Data Primary Examiner-Leland A.Sebastian Feb. 2, 1970 Austria 906/70 Assistant ExaminerB Hunt Attorney,Agent, or FirmMorgan, Finnegan, Durham [52] US. Cl 29/l82.5, 72/467,75/206 & Pi [51] Int. Cl B22f 5/00 [58] Field of Search... 75/206;29/182.5; 72/467 [57] ABSTRACT [56] Reierences Cited This inventionrelates to extrusion dies useful for pro UNITED STATES PATENTS cessmgboth non-ferrous metals and alloy steels, the

d1es bemg made of a predominant amount of molyb- 2,949,358 8/1960Alexander et a1. 75/206 denum or tungsten, the remainder being Zirconia3,271,142 9/1966 Hammond et al. 3,475,159 10/1969 Hansen 75/206 5Claims, N0 Drawings EXTRUSION DIE Extrusion dies for the processing ofvarious metals including non-ferrous metals and alloy steels, arewellknown. Conventional dies of this type are made from stellites andhigh temperature steels. Some dies are also made from such oxidematerials as zirconia. However, these materials have been found to bedisadvantageous. They are difficult to work and because of theirbrittleness they develop cracks during operation. Consequently, theiruseful life is quite short.

By means of this invention it is possible to prepare extrusion dieshaving sufficient ductility and an outstanding resistance to cracking.The dies of this invention contain from 85 to 98 percent by volume ofmolybdenum or tungsten with the remainder being a zirconia phase.Preferably, the molybdenum or tungsten phase will be in excess from 85to 95 percent by volume of the composition.

Mixtures of molybdenum and tungsten or alloys of molybdenum and tungstencan also be employed in place of molybdenum or tungsten alone.

The zirconia phase is preferably stabilized by a zirconia stabilizingoxide. Such zirconia stabilizing oxides include calcium oxide, magnesiumoxide and oxides of cerium and yttrium. Where employed, the stabilizingoxides are present in an amount of up to about 30 percent by volume ofthe zirconia phase.

The dies of this invention are prepared by conventional powdermetallurgical techniques. The powdered materials employed preferablyhave a particle size of from 0.1 to 30 microns. The powdered materialsare mixed together and then compressed to form compacts havingapproximately the desired final shape. The pressures employed can rangefrom 15,000 to 80,000 p.s.i. The pressed compacts are then sintered in areducing or inert atmosphere as, for example, in a hydrogen atmosphereor in an atmosphere of an inert gas such as helium or argon, or thelike. The sintering temperature should be from about l,700 to 2,200 C.If desired, pressure can be maintained during sintering, although it isnot required. Sintering time will depend upon the size and thickness ofthe compact but will generally range from about 2 to about 30 hours.After sintering and cooling, preferably while the inert or reducingatmosphere is maintained, the desired final form of the die is obtainedby machining to the final shape. More complex shapes can be made byspark erosion.

The final die produced in accordance with this invention has alongservice life and can be successfully used for the extrusion of steel ornon-ferrous metals. Furthermore, the nature of the die of this inventiongenerally eliminates the tendcncy of welding of the die to the extrudedmaterial. Consequently, it is generally possible, when using the dies ofthis invention, to dispense with the use oflubricants during extrusionwithout risking the likelihood of particles of extruded metal stickingto the die.

A suitable extrusion die can be manufactured by mixing 94.5 weight percent of fine molybdenum powder having a particle size of 4 microns, 5.1percent by weight of powdered zirconia having a particle size of l and0.4 weight per cent of magnesium oxide (magnesia) having a particle sizeof 0.1. Thereafter, the mixture is pressed to form a compact byapplication of pressure using conventional powder metallurgicaltechniques of 40,000 p.s.i. The pressed compacts are then sintered at2,000 C. for 8 hours in a hydrogen atmosphere. They are thereafterpermitted to cool in hydrogen and finally the final desired form of thedie is obtained by machining the sintered compacts.

What is claimed is:

1. An extrusion die for the processing of metallic materials, saidextrusion die consisting essentially in excess of percent by volume butnot more than percent by volume of molybdenum or tungsten, the remainderbeing a zirconia phase.

2. An extrusion die as in claim 1 wherein the zirconia phase containszirconia and one or more stabilizers for the zirconia.

3. An extrusion die as in claim 1 wherein the stabilizer for thezirconia phase is selected from among the oxides of calcium, magnesium,cerium and yttrium.

4. An extrusion die as in claim 1 consisting essentially of molybdenumand zirconia.

5. An extrusion die as in claim [consisting essentially of tungsten andzirconia.

2. An extrusion die as in claim 1 wherein the zirconia phase containszirconia and one or more stabilizers for the zirconia.
 3. An extrusiondie as in claim 1 wherein the stabilizer for the zirconia phase isselected from among the oxides of calcium, magnesium, cerium andyttrium.
 4. An extrusion die as in claim 1 consisting essentially ofmolybdenum and zirconia.
 5. An extrusion die as in claim 1 consistingessentially of tungsten and zirconia.